1. Field of the Invention
The present invention relates to a solid state imaging device and a manufacturing method for the same, and in particular to technology for blocking light between adjacent imaging pixels.
2. Description of the Related Art
In recent years, solid state imaging devices have been used in a wide range of devices including digital video cameras, digital still cameras, and mobile phones. One structure of a solid state imaging device is described below with reference to FIG. 1. The solid state imaging device shown in FIG. 1 is proposed in Japanese Patent Application Publication No. 2001-77339, and aims to suppress color mixing etc.
As shown in FIG. 1, the solid state imaging device includes a semiconductor substrate 900 and a gate insulation film 903 that has been formed on a main face thereof (in FIG. 3, the upper face in the Z axis direction). Photodiodes 901 having gaps therebetween have been formed at a boundary between the semiconductor substrate 900 and the gate insulation film 903. The photodiodes 901 are two-dimensionally arranged along the main face of the semiconductor substrate 900. Transfer channels 902 have been formed between pairs of adjacent photodiodes 901.
Polysilicon gates (hereinafter, called “PS gates”) 904 have been formed on the gate insulation film 903 in correspondence with the transfer channels 902, and an interlayer insulation film 905 and a light blocking film 906 have been formed so as to cover the PS gates 904. Note that apertures have been formed in the light blocking film 906 in correspondence with the photodiodes 901.
Light blocking walls 913 have been provided upright on the light blocking film 906. Insulation films 907 and planarizing films 909 have been formed in the spaces between the light blocking walls 913. Intra-layer lenses 908 have been formed at a boundary between the insulation films 907 and the planarizing films 909 in correspondence with the photodiodes 901. A protection film 914, a color filter 910, a planarizing film 911, and top lenses 912 have been formed in the stated order on the planarizing films 909 and the light blocking walls 913.
Japanese Patent Application Publication No. 2001-77339 discloses that stray light is prevented from entering adjacent imaging pixels by providing a light blocking wall 913 between the light blocking film 906 and the protection film 914 in each imaging pixel, thereby suppressing color mixing.
However, reliably preventing stray light from entering adjacent imaging pixels is difficult, even when the structure proposed in Japanese Patent Application Publication No. 2001-77339 is used. As shown in FIG. 1, in the solid state imaging device proposed by Japanese Patent Application Publication No. 2001-77339, the top edges of the light block walls 909 are located below the protection film 914, and there are cases in which light passing through the color filter 910 leaks into adjacent imaging pixels. A portion of the light that has leaked into an adjacent imaging pixel is reflected by a light blocking wall 913 and reaches the photodiode 901 of an imaging pixel into which the light was not intended to enter.
Such color mixing is particularly problematic in view of progress in reducing the size of imaging pixels while increasing the number of pixels. This problem arises from the fact that it is much more difficult to achieve a reduction in size in the thickness direction of the semiconductor substrate 900 than in a direction along the arrangement of the photodiodes 901.